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Updated: May 9, 2026
10:09
Adjustable Stiffness, External Fixator for the Rat Femur Osteotomy and Segmental Bone Defect Models
Published on: October 9, 2014
Relative stiffness, transverse displacement and dynamization in comparable external fixators.
1Oxford Orthopaedic Engineering Centre, Nuffield Orthopaedic Centre, Oxford, UK.
Clinical Biomechanics (Bristol, Avon)
|August 7, 2013
Summary
External fixators showed significant fracture movement under various loads, impacting healing potential. Even under weight-bearing, excessive motion and stress on bone and screws were observed.
Area of Science:
- Orthopedic biomechanics
- Surgical implant technology
Background:
- External fixation is a common orthopedic technique for fracture management.
- The stability of external fixator constructs is crucial for effective bone healing.
- Understanding construct behavior under physiological loading is essential.
Purpose of the Study:
- To evaluate the biomechanical performance of unilateral external fixators.
- To quantify fracture site movement under axial, bending, and torsional loads.
- To assess the impact of weight-bearing on fixator stability and stress distribution.
Main Methods:
- Laboratory testing of several unilateral external fixator devices.
- Application of simulated axial, bending, and torsional forces.
- Measurement of shear and axial displacement at the fracture site.
- Evaluation of construct stability under simulated full weight-bearing conditions.
Main Results:
- Substantial shear movement (up to 4 mm) was observed in some fixators.
- Shear displacement was consistently as significant as axial displacement across tested loads.
- All tested fixator/bone screw constructs exhibited excessive axial movement during simulated weight-bearing.
Conclusions:
- Unilateral external fixators demonstrate considerable instability under physiological loading.
- Excessive fracture site motion, particularly shear, may impede bone healing.
- High axial movement under weight-bearing can lead to detrimental bone and screw stresses, potentially nearing material yield points.
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